Polyester blend compositions and biodegradable films produced therefrom

1. A polyester blend composition comprising at least one branched biodegradable copolymer and at least one linear biodegradable copolymer wherein at least one of the linear biodegradable copolymers is selected from the group consisting of:

an aromatic polyester copolymer (a) having repeating units comprising an acid component and a glycol component; wherein the acid component comprises about 50 to 90 mol % of copolymerized terephthalic acid, about 0.2 to 6 mol % of copolymerized sulfonic acid metal salt, and about 9.8 to 49.8 mol % of copolymerized aliphatic dicarboxylic acid or a copolymerized ester-forming derivative of the aliphatic dicarboxylic acid; and wherein the glycol component comprises about 50 to 99.9 mol % of copolymerized ethylene glycol and about 0.1 to 50 mol % of copolymerized diethylene glycol; and

a polyester copolymer (b) prepared by copolymerization of said copolymer (a) with a poly(alkylene ether) glycol; and

wherein at least one of the branched biodegradable copolymers is a branched polyester copolymer (c), and wherein said branched polyester copolymer (c) is prepared by polycondensation of said copolymer (a) with a poly(alkylene ether) glycol.

2. A polyester blend composition of comprising at least one branched biodegradable copolymer and at least one linear biodegradable copolymer wherein at least one of the linear copolymers comprises:

an aromatic polyester copolymer consisting essentially of repeating units comprising an acid component and a glycol component; wherein the acid component comprises about 50 to 90 mol % of copolymerized terephthalic acid, about 0.2 to 6 mol % of copolymerized sulfonic acid metal salt, and about 9.8 to 49.8 mol % of copolymerized aliphatic dicarboxylic acid or a copolymerized ester-forming derivative of the aliphatic dicarboxylic acid; and wherein the glycol component comprises about 50 to 99.9 mol % of copolymerized ethylene glycol and about 0.1 to 50 mol % of copolymerized diethylene glycol;

wherein at least one of the branched copolymers is a branched polyester copolymer, and wherein said branched polyester copolymer is prepared by polycondensation of said aromatic polyester copolymer with a poly(alkylene ether) glycol.

3. A polyester blend composition comprising at least one branched aromatic biodegradable copolymer and at least one linear aromatic biodegradable copolymer, wherein at least one of the linear copolymers is selected from the group consisting of:

an aromatic polyester copolymer (a) having repeating units comprising an acid component and a glycol component; wherein the acid component comprises about 50 to 90 mol % of copolymerized terephthalic acid, about 0.2 to 6 mol % of copolymerized sulfonic acid metal salt, and about 9.8 to 49.8 mol % of copolymerized aliphatic dicarboxylic acid or a copolymerized ester-forming derivative of the aliphatic dicarboxylic acid; and wherein the glycol component comprises about 50 to 99.9 mol % of copolymerized ethylene glycol and about 0.1 to 50 mol % of copolymerized diethylene glycol; and

a polyester copolymer (b) prepared by copolymerization of said copolymer (a) with a poly(alkylene ether) glycol; and

wherein at least one of the branched copolymers is said branched polyester copolymer (c), and wherein said branched polyester copolymer (c) is prepared by polycondensation of said copolymer (a) with a poly(alkylene ether) glycol.

4. A polyester blend composition comprising at least one branched aromatic biodegradable copolymer and at least one linear aromatic biodegradable copolymer, wherein at least one of the linear copolymers is selected from the group consisting of:

an aromatic polyester copolymer (a) consisting essentially of repeating units comprising an acid component and a glycol component; wherein the acid component comprises about 50 to 90 mol % of copolymerized terephthalic acid, about 0.2 to 6 mol % of copolymerized sulfonic acid metal salt, and about 9.8 to 49.8 mol % of copolymerized aliphatic dicarboxylic acid or a copolymerized ester-forming derivative of the aliphatic dicarboxylic acid; and wherein the glycol component comprises about 50 to 99.9 mol % of copolymerized ethylene glycol and about 0.1 to 50 mol % of copolymerized diethylene glycol; and

a polyester copolymer (b) prepared by copolymerization of said copolymer (a) with a poly(alkylene ether) glycol; and

wherein at least one of the branched copolymers consists of:

a branched polyester copolymer (c) prepared by polycondensation of said copolymer (a) with a poly(alkylene ether) glycol.

5. A polyester blend composition consisting essentially of at least one linear copolymer selected from the group consisting of:

an aromatic polyester copolymer (a) having repeating units comprising an acid component and a glycol component; wherein the acid component comprises about 50 to 90 mol % of copolymerized terephthalic acid, about 0.2 to 6 mol % of copolymerized sulfonic acid metal salt, and about 9.8 to 49.8 mol % of copolymerized aliphatic dicarboxylic acid or a copolymerized ester-forming derivative of the aliphatic dicarboxylic acid; and wherein the glycol component comprises about 50 to 99.9 mol % of copolymerized ethylene glycol and about 0.1 to 50 mol % of copolymerized diethylene glycol; and

a polyester copolymer (b) prepared by copolymerization of said copolymer (a) with a poly(alkylene ether) glycol; and

a branched polyester copolymer (c) prepared by polycondensation of said copolymer (a) with a poly(alkylene ether) glycol.

6. A polyester blend composition comprising at least two copolymers selected from the group consisting of:

an aromatic polyester copolymer (a) consisting essentially of repeating units comprising an acid component and a glycol component; wherein the acid component comprises about 50 to 90 mol % of copolymerized terephthalic acid, about 0.2 to 6 mol % of copolymerized sulfonic acid metal salt, and about 9.8 to 49.8 mol % of copolymerized aliphatic dicarboxylic acid or a copolymerized ester-forming derivative of the aliphatic dicarboxylic acid; and wherein the glycol component comprises about 50 to 99.9 mol % of copolymerized ethylene glycol and about 0.1 to 50 mol % of copolymerized diethylene glycol;

a polyester copolymer (b) prepared by copolymerization of said copolymer (a) with a poly(alkylene ether) glycol; and

a branched polyester copolymer (c) prepared by polycondensation of said copolymer (a) with a poly(alkylene ether) glycol.

7. The blend composition of claim 6 that comprises at least 1 wt % of at least one of said copolymers (b) and (c), and less than 99 wt % of said copolymer (a).

8. The blend composition of claim 6 that comprises at least 10 wt % of at least one of said copolymers (a) and (c), and less than 90 wt % of said copolymer (b).

9. The blend composition of claim 6 that comprises at least 0.1 wt % of at least one of said copolymers (a) and (b), and less than 99.9 wt % of said copolymer (c).

10. The blend composition of any of claims 1 , or, wherein the acid component of said copolymer (a) is 70 to 90 mol % of copolymerized terephthalic acid.

11. The blend composition of any of claims 1 , or, wherein the copolymerized poly(alkylene ether) glycol of said copolymer (b) is 0.1 to 20 wt % of said copolymer (b).

12. The blend composition of any of claims 1 , 3 , or 4 , wherein the polycondensed poly(alkylene ether) glycol of said copolymer (c) is 0.1 to 20 wt % of said copolymer (c).

13. The blend composition of any of claims 1 , or, wherein said copolymerized poly(alkylene ether) glycol, said polycondensed poly(alkylene ether) glycol, or said copolymerized and said polycondensed poly(alkylene ether) glycols are poly(ethylene glycol).

14. A biodegradable film formed from the blend composition of any of claims 1 , 5 , 6 , or 2 .

15. The film of claim 14 , wherein the film has a tear strength of at least 80 gf.

16. The film of claim 14 , wherein the film has a tensile elongation of at least 300%.

17. A process for forming a biodegradable blend composition having softness and tear strength properties adequate for formation of films using blowing processes comprising blending at least two copolymers selected from the group consisting of:

an aromatic polyester copolymer (a) consisting essentially of repeating units comprising an acid component and a glycol component; wherein the acid component comprises about 50 to 90 mol % of copolymerized terephthalic acid, about 0.2 to 6 mol % of copolymerized sulfonic acid metal salt, and about 9.8 to 49.8 mol % of copolymerized aliphatic dicarboxylic acid or a copolymerized ester-forming derivative of the aliphatic dicarboxylic acid; and wherein the glycol component comprises about 50 to 99.9 mol % of copolymerized ethylene glycol and about 0.1 to 50 mol % of copolymerized diethylene glycol;

a polyester copolymer (b) prepared by copolymerization of said copolymer (a) with a poly(alkylene ether) glycol; and

a branched polyester copolymer (c) prepared by polycondensation of said copolymer (a) with a poly(alkylene ether) glycol.

18. A process for producing a biodegradable film, comprising:

blending at least one branched biodegradable polyester copolymer and at least one linear biodegradable polyester copolymer and then blow-molding the resulting blend to form said film, wherein at least one of the linear copolymers is selected from the group consisting of:

an aromatic polyester copolymer (a) having repeating units comprising an acid component and a glycol component; wherein the acid component comprises about 50 to 90 mol % of copolymerized terephthalic acid, about 0.2 to 6 mol % of copolymerized sulfonic acid metal salt, and about 9.8 to 49.8 mol % of copolymerized aliphatic dicarboxylic acid or a copolymerized ester-forming derivative of the aliphatic dicarboxylic acid; and wherein the glycol component comprises about 50 to 99.9 mol % of copolymerized ethylene glycol and about 0.1 to 50 mol % of copolymerized diethylene glycol; and

a polyester copolymer (b) prepared by copolymerization of said copolymer (a) with a poly(alkylene ether) glycol;

wherein at least one of the branched copolymers is a branched polyester copolymer (c) prepared by polycondensation of said copolymer (a) with a poly(alkylene ether) glycol.

19. A process for improving at least one of the wrinkling and the tear strength of a film made from an aromatic polyester copolymer (a) consisting essentially of repeating units comprising an acid component and a glycol component; wherein the acid component comprises about 50 to 90 mol % of copolymerized terephthalic acid, about 0.2 to 6 mol % of copolymerized sulfonic acid metal salt, and about 9.8 to 49.8 mol % of copolymerized aliphatic dicarboxylic acid or a copolymerized ester-forming derivative of the aliphatic dicarboxylic acid; and wherein the glycol component comprises about 50 to 99.9 mol % of copolymerized ethylene glycol and about 0.1 to 50 mol % of copolymerized diethylene glycol, said process comprising blending said copolymer (a) prior to forming said film with at least one copolymer selected from the group consisting of:

a polyester copolymer (b) prepared by copolymerization of said copolymer (a) with a poly(alkylene ether) glycol; and

a branched polyester copolymer (c) prepared by polycondensation of said copolymer (a) with a poly(alkylene ether) glycol.

20. A process for improving at least one of the wrinkling and the tear strength of a film made from an aromatic polyester copolymer (a) consisting essentially of repeating units comprising an acid component and a glycol component; wherein the acid component comprises about 50 to 90 mol % of copolymerized terephthalic acid, about 0.2 to 6 mol % of copolymerized sulfonic acid metal salt, and about 9.8 to 49.8 mol % of copolymerized aliphatic dicarboxylic acid or a copolymerized ester-forming derivative of the aliphatic dicarboxylic acid; and wherein the glycol component comprises about 50 to 99.9 mol % of copolymerized ethylene glycol and about 0.1 to 50 mol % of copolymerized diethylene glycol, said process comprising blending said copolymer (a) prior to forming said film with at least one copolymer consisting of:

a branched polyester copolymer (c) prepared by polycondensation of said copolymer (a) with a poly(alkylene ether) glycol.